The present invention relates to a hose with interlocked profile, particularly for automotive exhaust systems, helically stripwound from a least one single-layer or multi-layer metal strip, pre-formed to the shape of an S, with the edges of adjacent strip windings being interlocked with each other by means of the legs of the pre-form which have the aspect of the S-shaped hooks, and by means of folded end rims.
Conventional hoses with interlocked profile are available, in particular, in two different versions, i.e. with circular cross section and with polygonal cross section. Hoses with interlocked profile and circular cross section have a particularly high leakage resistance, but they tend to unwind, i.e. to break the interlocked connection in a direction opposite to the winding direction. For this reason, adjacent interlocked edges have to be connected firmly with each other in an appropriate way. This is accomplished, for example according to EP 0 523 341, by means of a compressed stiffening corrugation running from radial inside to radial outside.
The leakage resistance of hoses with interlocked profile and polygonal cross section is not as high, but such hoses have the advantage of allowing their rigidity to be adapted, i.e. their capability of decoupling vibrations from adjacent components of an assembly, due to a varying tightness in winding. The polygon edges maintain the original shape and to winding structure of the hose and minimize the tendency to unwinding.
The above-described hoses with interlocked profile are applied either individually as an exhaust line, particularly for trucks, or as a liner combined with a surrounding metal bellows, particularly for exhaust systems in other automotive applications. In the latter case, the metal bellows is the component, which makes the exhaust line resistant to leakage.
Hoses with interlocked profile and polygonal cross section are preferably applied in automotive exhaust systems due to the better adaptability of their rigidity. Depending on the installation conditions and installation position of the engine with which the hose with interlocked profile is connected, what may be required is a very loose winding of the hose with interlocked profile for the purpose of minimizing its rigidity, which means an optimization of its vibration decoupling capacity. Such a loose winding will cause a tendency to the development of noise in operation, since the hose can be shifted by such a distance that it may hit a potentially installed coaxial bellows, or that the adjacent edges which are interlocked under clearance, i.e. the legs and folded rims, may hit each other. At present, attempts are made to avoid the development of noise by means of providing a damping insert between hose with interlocked profile and bellows, for example a wire mesh, which will avoid the direct contact between hose and bellows and restrict the shifting movement of the hose, so that the relative movements of the adjacent interlocked folded edges are reduced.
The only way of solving the problem of noise totally would be to manufacture the hose in tighter windings, thus reducing the clearance in the interlocked sections and also the movability of the hose. Another result, however, would be an increase in deficiency work of the hose, whose reduction was the reason for manufacturing the hose in loose windings.